// 由于默认的远天空盒,在相机移动到地面上后会变偏,所以需要设置近天空盒
import * as Cesium from 'cesium';

const BoxGeometry = Cesium.BoxGeometry;
const Cartesian3 = Cesium.Cartesian3;
const defaultValue = Cesium.defaultValue;
const defined = Cesium.defined;
const destroyObject = Cesium.destroyObject;
const DeveloperError = Cesium.DeveloperError;
const GeometryPipeline = Cesium.GeometryPipeline;
const Matrix3 = Cesium.Matrix3;
const Matrix4 = Cesium.Matrix4;
const Transforms = Cesium.Transforms;
const VertexFormat = Cesium.VertexFormat;
const BufferUsage = Cesium.BufferUsage;
const CubeMap = Cesium.CubeMap;
const DrawCommand = Cesium.DrawCommand;
const loadCubeMap = Cesium.loadCubeMap;
const RenderState = Cesium.RenderState;
const VertexArray = Cesium.VertexArray;
const BlendingState = Cesium.BlendingState;
const SceneMode = Cesium.SceneMode;
const ShaderProgram = Cesium.ShaderProgram;
const ShaderSource = Cesium.ShaderSource;
//片元着色器，直接从源码复制
const SkyBoxFS =
    "uniform samplerCube u_cubeMap;\n\
varying vec3 v_texCoord;\n\
void main()\n\
{\n\
vec4 color = textureCube(u_cubeMap, normalize(v_texCoord));\n\
gl_FragColor = vec4(czm_gammaCorrect(color).rgb, czm_morphTime);\n\
}\n\
";



//顶点着色器有修改，主要是乘了一个旋转矩阵
const SkyBoxVS =
    "attribute vec3 position;\n\
varying vec3 v_texCoord;\n\
uniform mat3 u_rotateMatrix;\n\
void main()\n\
{\n\
vec3 p = czm_viewRotation * u_rotateMatrix * (czm_temeToPseudoFixed * (czm_entireFrustum.y * position));\n\
gl_Position = czm_projection * vec4(p, 1.0);\n\
v_texCoord = position.xyz;\n\
}\n\
";

/**
 * 为了兼容高版本的Cesium，因为新版cesium中getRotation被移除
 */
if (!Cesium.defined(Cesium.Matrix4.getRotation)) {
    Cesium.Matrix4.getRotation = Cesium.Matrix4.getMatrix3;
}

function SkyBoxOnGround(options) {
    /**
     * 近景天空盒
     * @type Object
     * @default undefined
     */
    this.sources = options.sources;
    this._sources = undefined;

    /**
     * Determines if the sky box will be shown.
     *
     * @type {Boolean}
     * @default true
     */
    this.show = defaultValue(options.show, true);

    this._command = new DrawCommand({
        modelMatrix: Matrix4.clone(Matrix4.IDENTITY),
        owner: this
    });
    this._cubeMap = undefined;

    this._attributeLocations = undefined;
    this._useHdr = undefined;
}

const skyboxMatrix3 = new Matrix3();
SkyBoxOnGround.prototype.update = function (frameState, useHdr) {
    const that = this;

    if (!this.show) {
        return undefined;
    }

    if (
        frameState.mode !== SceneMode.SCENE3D &&
        frameState.mode !== SceneMode.MORPHING
    ) {
        return undefined;
    }

    if (!frameState.passes.render) {
        return undefined;
    }

    const context = frameState.context;

    if (this._sources !== this.sources) {
        this._sources = this.sources;
        const sources = this.sources;

        if (!defined(sources.positiveX) ||
            !defined(sources.negativeX) ||
            !defined(sources.positiveY) ||
            !defined(sources.negativeY) ||
            !defined(sources.positiveZ) ||
            !defined(sources.negativeZ)
        ) {
            throw new DeveloperError(
                "this.sources is required and must have positiveX, negativeX, positiveY, negativeY, positiveZ, and negativeZ properties."
            );
        }

        if (
            typeof sources.positiveX !== typeof sources.negativeX ||
            typeof sources.positiveX !== typeof sources.positiveY ||
            typeof sources.positiveX !== typeof sources.negativeY ||
            typeof sources.positiveX !== typeof sources.positiveZ ||
            typeof sources.positiveX !== typeof sources.negativeZ
        ) {
            throw new DeveloperError(
                "this.sources properties must all be the same type."
            );
        }

        if (typeof sources.positiveX === "string") {
            // Given urls for cube-map images.  Load them.
            loadCubeMap(context, this._sources).then(function (cubeMap) {
                that._cubeMap = that._cubeMap && that._cubeMap.destroy();
                that._cubeMap = cubeMap;
            });
        } else {
            this._cubeMap = this._cubeMap && this._cubeMap.destroy();
            this._cubeMap = new CubeMap({
                context: context,
                source: sources
            });
        }
    }

    const command = this._command;

    const modelMatrix = Transforms.eastNorthUpToFixedFrame(
        frameState.camera._positionWC
    );
    if (!defined(command.vertexArray)) {
        command.uniformMap = {
            u_cubeMap: function () {
                return that._cubeMap;
            },
            u_rotateMatrix: function () {
                return Matrix4.getRotation(modelMatrix, skyboxMatrix3);
            }
        };

        const geometry = BoxGeometry.createGeometry(
            BoxGeometry.fromDimensions({
                dimensions: new Cartesian3(2.0, 2.0, 2.0),
                vertexFormat: VertexFormat.POSITION_ONLY
            })
        );
        const attributeLocations = (this._attributeLocations = GeometryPipeline.createAttributeLocations(
            geometry
        ));

        command.vertexArray = VertexArray.fromGeometry({
            context: context,
            geometry: geometry,
            attributeLocations: attributeLocations,
            bufferUsage: BufferUsage._DRAW
        });

        command.renderState = RenderState.fromCache({
            blending: BlendingState.ALPHA_BLEND
        });
    }

    if (!defined(command.shaderProgram) || this._useHdr !== useHdr) {
        const fs = new ShaderSource({
            defines: [useHdr ? "HDR" : ""],
            sources: [SkyBoxFS]
        });
        command.shaderProgram = ShaderProgram.fromCache({
            context: context,
            vertexShaderSource: SkyBoxVS,
            fragmentShaderSource: fs,
            attributeLocations: this._attributeLocations
        });
        this._useHdr = useHdr;
    }

    if (!defined(this._cubeMap)) {
        return undefined;
    }

    return command;
};
SkyBoxOnGround.prototype.isDestroyed = function () {
    return false;
};
SkyBoxOnGround.prototype.destroy = function () {
    const command = this._command;
    command.vertexArray = command.vertexArray && command.vertexArray.destroy();
    command.shaderProgram =
        command.shaderProgram && command.shaderProgram.destroy();
    this._cubeMap = this._cubeMap && this._cubeMap.destroy();
    return destroyObject(this);
};

export default SkyBoxOnGround;